In the past, a method of arranging a transfer member with a hairline-shaped relief in a mold to form a hairline pattern on the surface of a shaped article by using in-mold shaping has been known (for example, see Patent Literature 1). However, this method requires a transfer member, so is unsuited for mass production of shaped articles.
Also, a method of rubbing the surface of a mold by sandpaper or a metal brush to form a large number of extremely fine grooves and thereby obtain a shaped article with a hairline pattern corresponding to the extremely fine grooves without using a transfer member has been known (for example, see Patent Literature 2).
However, in the method described in Patent Literature 2, since sandpaper or a metal brush is used to form the extremely fine grooves, there is a large variation in the surface shape of each mold. Therefore, it is difficult to obtain the hairline pattern of the same shape in the case of using different molds, and thus the product shapes are not stable.
Patent Literature 1
Japanese Unexamined Patent Publication No. 1-141014 A
Patent Literature 2
Japanese Unexamined Patent Publication No. 10-71677 A